The present invention relates to an information processing system connected to the Internet. More specifically the present invention relates to a system and method for protecting information stored within a system from unauthorized tampering from inside or outside the system.
In recent years, mutually connected computer equipment is being utilized for a variety of applications due to the spread of the Internet. Methods such as the following have been implemented as a means to prevent illegal access to these kinds of computers. The most typical protection means is illustrated in FIG. 12. A system called a firewall is connected between the information processing system and the Internet. Services provided over the Internet can be limited by using the firewall to reject unauthorized access.
The computer equipment providing the service is installed outside the firewall as shown in FIG. 13, and in some cases protective measures are also installed on the computer equipment. Technology for installing a mail server external to the firewall in a system such as shown in FIG. 13 is disclosed in JP-A No. H11-266279. In a system of this kind, the user on the external side of the firewall can send or receive mail without using the firewall, and security within the firewall is enhanced.